Hello, Jon, and
As our late member and Waffen-SS veteran HaEn wrote on page 1 of this thread: "At the front there was very little marching, just a lot of crawling, running, slushing through mud, taking cover, and very little incentive for singing."
By the time Volksgrenadier and Volkssturm units were formed, the front was everywhere. Not much time for singing.
The so-called "Volkssturmlied" you may find on YouTube is NOT a "Volkssturmlied". It is a 1940 recording of the 1933 song "Volk an's Gewehr" (an arrangement by Hanns Steinkopf). The YouTube title was made-up by the uploader, as he actually admitted himself.
There is no song called "Im ganzen Vaterland", it is another recently made-up title. The real title of that song is "Die Jägerbraut
" (The Hunter's Bride). It was composed in the mid-1930s, recorded several times in the 1960s/1970s and it has nothing to do with the Volksgrenadiere.
There are no compositions known to me associated with the Volksgrenadiere.
I know of only two (real) compositions associated with the Volkssturm: "Lied des schlesischen Volkssturms" and "Marsch der Volkssturm-Bataillone". But it is highly unlikely that anyone outside the Rundfunk, that is, in the field, actually sang or played them. (There were probably more songs written for the Volkssturm, by the German propaganda, but they're all basically unknown today and it's unlikely that the Volkssturm ever actually sang them.) People got sick of military music already in 1942, let alone at the end of the war.